LONDON (AFP) - Britain organised a flypast and 140,000 people sent cards to mark the 100th birthday on Thursday (April 30) of a World War II veteran whose staggering fund-raising efforts inspired a country in the depths of a coronavirus outbreak.

Having served Britain in the last century, Captain Tom Moore has thrust himself into the thick of its latest battle by doing laps of his garden to raise money for health service charities.

At the latest tally, he had raised more than £30 million (S$52.8 million) to help support staff and volunteers working on the coronavirus effort in the state-run National Health Service (NHS).

Capt Moore's efforts and humility have propelled him to iconic status, with a high-speed train named after him and all letters sent in the British postal service this week carrying a birthday message.

Prime Minister Boris Johnson, Prince Charles and England football captain Harry Kane were among those who offered their congratulations for his 100th birthday.

Cards from around the world filled the vast hall of his grandson Benjie's school, and thousands of children have sent him their drawings.

"Your heroic efforts have lifted the spirits of the entire nation," said Mr Johnson, who recently recovered from coronavirus, in a video message.

"You've created a channel to enable millions to say a heartfelt thank you to the remarkable men and women in our NHS who are doing a most astounding job."

On Thursday morning, Royal Air Force pilots flew a Spitfire and a Hurricane, usually deployed for WWII commemorative events, over Capt Moore's home in Bedfordshire, north of London.

Live television footage showed the veteran in his garden, smartly dressed in a jacket and tie with his medals on his chest, waving as they went past.

"I remember when they were flying not with peace, but with anger," he told the BBC.

Separately, the army announced it was making Capt Moore an honorary colonel, an appointment approved by Queen Elizabeth II, calling him an "inspirational role model to generations young and old".

"I never, ever anticipated ever in my life anything like this," Capt Moore said of the support, thanking everyone who sent him messages.

He offered his own congratulations for Mr Johnson's new baby boy, who was born on Wednesday, saying: "Well done, prime minister!"

Capt Moore said he was "very moved by" being made an honorary colonel, adding: "I'm still Captain Tom, that's who I really am. But if people choose to call me 'colonel', well, thank you very much."

Capt Moore's latest mission began on April 6, with the target of raising £1,000 for NHS charities as a thank you for the treatment he received while suffering from cancer and a broken hip.

The former engineer, who served in India and Myanmar, planned to raise the money by completing 100 laps of his 25m garden, asking for sponsorship online.

But the generosity of the public far exceeded his hopes, and he received millions within days.

Capt Moore completed the final leg of his journey just 10 days later, crossing the line with the aid of his walking frame and a military guard of honour.

He now owns two world records: Raising the most money ever doing an individual charity walk and the oldest person ever to get a number one single in the UK charts.

His unlikely ascent to the top of the pop charts came with a charity version of musical classic and popular football chant You'll Never Walk Alone, in which he sings along with British stage star Michael Ball and the NHS choir.

"We are hugely proud of how the nation has taken granddad to its heart," said grandson Benjie.

"Words can't express how much I idolise him."